Replace crossbeam with std's scoped threads

Cargo.lock

@@ -247,20 +247,6 @@ dependencies = [
  "cfg-if",
 ]
 
-[[package]]
-name = "crossbeam"
-version = "0.8.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2801af0d36612ae591caa9568261fddce32ce6e08a7275ea334a06a4ad021a2c"
-dependencies = [
- "cfg-if",
- "crossbeam-channel",
- "crossbeam-deque",
- "crossbeam-epoch",
- "crossbeam-queue",
- "crossbeam-utils",
-]
-
 [[package]]
 name = "crossbeam-channel"
 version = "0.5.6"
@@ -296,16 +282,6 @@ dependencies = [
  "scopeguard",
 ]
 
-[[package]]
-name = "crossbeam-queue"
-version = "0.3.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1cd42583b04998a5363558e5f9291ee5a5ff6b49944332103f251e7479a82aa7"
-dependencies = [
- "cfg-if",
- "crossbeam-utils",
-]
-
 [[package]]
 name = "crossbeam-utils"
 version = "0.8.11"
@@ -1178,7 +1154,6 @@ dependencies = [
 name = "proc-macro-srv"
 version = "0.0.0"
 dependencies = [
- "crossbeam",
  "expect-test",
  "libloading",
  "mbe",

crates/proc-macro-srv/Cargo.toml

@@ -24,7 +24,6 @@ tt = { path = "../tt", version = "0.0.0" }
 mbe = { path = "../mbe", version = "0.0.0" }
 paths = { path = "../paths", version = "0.0.0" }
 proc-macro-api = { path = "../proc-macro-api", version = "0.0.0" }
-crossbeam = "0.8.1"
 
 [dev-dependencies]
 expect-test = "1.4.0"

crates/proc-macro-srv/src/lib.rs

@@ -26,6 +26,7 @@ use std::{
     ffi::OsString,
     fs,
     path::{Path, PathBuf},
+    thread,
     time::SystemTime,
 };
 
@@ -65,18 +66,16 @@ impl ProcMacroSrv {
 
         let macro_body = task.macro_body.to_subtree();
         let attributes = task.attributes.map(|it| it.to_subtree());
-        // FIXME: replace this with std's scoped threads once they stabilize
-        // (then remove dependency on crossbeam)
-        let result = crossbeam::scope(|s| {
-            let res = match s
-                .builder()
+        let result = thread::scope(|s| {
+            let thread = thread::Builder::new()
                 .stack_size(EXPANDER_STACK_SIZE)
                 .name(task.macro_name.clone())
-                .spawn(|_| {
+                .spawn_scoped(s, || {
                     expander
                         .expand(&task.macro_name, &macro_body, attributes.as_ref())
                         .map(|it| FlatTree::new(&it))
-                }) {
+                });
+            let res = match thread {
                 Ok(handle) => handle.join(),
                 Err(e) => std::panic::resume_unwind(Box::new(e)),
             };
@@ -86,10 +85,6 @@ impl ProcMacroSrv {
                 Err(e) => std::panic::resume_unwind(e),
             }
         });
-        let result = match result {
-            Ok(result) => result,
-            Err(e) => std::panic::resume_unwind(e),
-        };
 
         prev_env.rollback();